From @FROGGS

grammar D { our token doo { doo }; }; say 'doo' ~~ &D​::doo
rakudo-moar a6f563​: OUTPUT«Type check failed in binding <anon>; expected 'D' but got 'Cursor'␤ in regex doo at /tmp/8wglQQkyMB​:1␤ in block <unit> at /tmp/8wglQQkyMB​:1␤␤»

grammar D { token doo is export { doo }; }; import D; say 'doo' ~~ &doo
rakudo-moar a6f563​: OUTPUT«Type check failed in binding <anon>; expected 'D' but got 'Cursor'␤ in regex doo at /tmp/anZydiSimC​:1␤ in block <unit> at /tmp/anZydiSimC​:1␤␤»

It works when we mess with the invocant​:
grammar D { our token doo(Mu​:) { doo }; }; say 'doo' ~~ &D​::doo
rakudo-moar a6f563​: OUTPUT«｢doo｣␤»

grammar D { token doo(Mu​:) is export { doo }; }; import D; say 'doo' ~~ &doo
rakudo-moar a6f563​: OUTPUT«｢doo｣␤»

grammar D { our token doo(Mu​:) { doo }; }; say 'doo' ~~ / <&D​::doo> /
rakudo-moar a6f563​: OUTPUT«｢doo｣␤»

It should work without "restricting" the invocant to Mu.

From @FROGGS

Patch​: rakudo/rakudo@88b1203c05
Tests​: Raku/roast@b159d9b862

The code above about 'token is export' is not meant to work IMO, compare to how 'method is export' is called.

@FROGGS - Status changed from 'new' to 'resolved'